In recent years, the application of secondary batteries to hybrid applications with engines of locomotives, buses, construction machines, or the like or to power fluctuation suppression applications in stationary type industrial equipment has become active. In these applications, input and output of a large electric current, and a charging state range where energy can be used in a wide range are required. Conventionally, in order to use an energy capacity capable of being used for storage or traveling without waste, a technique for controlling an upper or lower limit of a charging state range where energy of a secondary battery can be used by specifying the limits using an electric capacity has been widely used. However, in situations where the charging state range is specified using the electric capacity to be set in a wide range, before reaching the upper or lower limit electric capacity, an upper or lower limit value of a closed-circuit voltage of the battery may arrive, so that the equipment may stop. That is, a usable energy range may be greatly limited. In this way, there may be situations where a voltage of a secondary battery cannot be accurately limited.
In order to solve the above-mentioned problem, an object of the invention is to provide a power control apparatus and a power control system capable of accurately limiting a voltage of a secondary battery.